34 HUMBLE CREATURES. 



LETTER V. 



TEE ANTENNA OR PEBLBKS OF THE FLY ; THEIR STBITCTUBE, 

 AND VARIOUS THBOBIES EEGARDING THEIR FUNCTIONS.— 

 THE EYES, COMPOUND AND SIMPLE ; THEIR STRUCTURE ANI) 

 USES. 



There is perhaps not a more interesting object ia the 

 animal creation than the head of a common House- 

 fly. If you take a lens, and examine it carefully, you 

 will find in front of the forehead a pair of short 

 antennae or feelers (PI. IV. fig. 1, a, a), organs which, 

 in some of the insect races, impart those wonderful 

 instinctive properties that have in this respect raised 

 their possessors to a level with the so-called higher 

 animals, and have rendered them a complete mystery 

 to the naturalist. 



The antennse of a fly are well worthy of a particular 

 description ; they are composed apparently of three, 

 but really of six joints, the third of which (PI. VI.fig.2) 

 is dilated and much larger than the rest ; whilst the 

 sixth is furnished with an arborescent tuft of bristles, 

 and is termed a plumose joint. 



When the fly is at rest, the first three joints lie in 

 a depression of the insect's head (PL IV. fig. 1, a, a), 

 whilst the plumose joint is seen to protrude : the 



